What are some things that you'd build with Unity that aren't games?

Not OP, but at £JOB, I use Unity most of the time making demo and sales apps for clients to use at shows. The fact that it can build for basically every common platform and (most of the time) not need any special considerations for that makes it ideal for us. Sure, we could write web apps or something, but that's a different department.

I'm also not sure if it's still in the installer, but it used to ask you what you would be using unity for, and I don't remember most of the options, but one of them was "military simulations" or something like that, so they are aware of the possibility

User interfaces for complex physical plants.

https://en.wikipedia.org/wiki/Digital_twin